This invention is directed to a compression heat transfer system containing refrigerants and lubricants wherein there is partial to near immiscibility of one in the other at above a certain temperature. The lubricant or lubricant-rich phase (where there is some miscibility of the lubricant and refrigerant) resides on the bottom of the refrigerant or refrigerant-rich phase (where there is some miscibility of the lubricant and refrigerant).
Compression heat transfer system designers must consider lubricant circulation and return of the lubricant to a sump or reservoir when designing and evaluating a refrigeration system. The primary function of the lubricant is to lubricate and seal compressor components. In some applications, such as an oil flooded rotary screw compressor, the lubricant also functions as a heat transfer medium, removing the heat of compression. Design of the refrigeration system must include a method to keep the majority of the lubricant in the compressor, and to provide a means to return, in an efficient manner, the oil which has entered the refrigeration system back to the reservoir.
Chlorofluorocarbon compounds, generally referred to in the industry as CFCs are comprised entirely of carbon, chlorine and fluorine, but no presence of hydrogen atoms. Molecules that also contain hydrogen are designated as HCFCs. Molecules containing only carbon, hydrogen and fluorine, but no presence of chlorine, are designated as HFCs.
U.S. Pat. No. 4,851,144 (McGraw et al., Jul. 25, 1989) relates to lubricant base compositions for compression refrigeration that are composed of 95 to 5% by weight of polyether polyols having a number average molecular weight from about 400 to about 5,000 and 5 to 95% of esters made from polyhydric alcohols with alkanoic acids or esters made from alkanedioic acids with alkanols. A refrigeration fluid is made from the base composition with the addition of selected hydrochlorofluorocarbons and hydrofluorocarbons so that the base composition is miscible with the refrigerant in the range from xe2x88x9220xc2x0 C. to greater than 65xc2x0 C.
U.S. Pat. No. 4,948,525 (Sasaki et al., Aug. 14, 1990) discloses a lubricating oil composition for a refrigerator using therein 1,1,1,2-tetrafluoroethane as the refrigerant, comprising as the base oil a polyoxyalkylene glycol monoether of the following general formula
R1xe2x80x94(OR2)mxe2x80x94OH
wherein R1 is an alkyl group having 1-18 carbon atoms, m is an integer of 5-70, R2 is an alkylene group having 2-4 carbon atoms and a ratio of 0-0.8 between (the number of xe2x80x94OR2xe2x80x94 group wherein R2 is ethylene group)/m in the molecule, the polyoxyalkylene glycol monoether having a specified pour point and a specified kinematic viscosity. In one embodiment, the lubricating oil composition may further comprise a specified phosphate and at least one kind of a specified epoxy compound to further improve the oil composition in properties.
U.S. Pat. No. 5,027,606 (Short, Jul. 2, 1991) relates to a rotary displacement compression heat transfer system and method for improving its efficiency which includes a rotary displacement compressor for compressing a refrigerant, a condenser connected with the outlet of the compressor, an evaporator connected with the inlet of the compressor, an oil pump for injecting oil into the compressor, an oil separator for separating out the oil and recirculating it to the compressor, a non-chlorinated hydrocarbon refrigerant, and a synthetic oil ingredient in the oil providing an inverse solubility characteristic where a mixture of the refrigerant and oil has two immiscible phases in the compressor""s operating temperature range and has only one dissolved liquid phase at a temperature in the evaporator""s operating range at a weight concentration of oil less than about 5%.
U.S. Pat. No. 5,185,092 (Fukuda et al., Feb. 9, 1993) describes a lubricating oil for refrigerators using 1,1,1,2-tetrafluoroethane refrigerant. Having esters as base oil, its viscosity range is between 2-30 mm/s at 100xc2x0 C. By adding esters alone or by adding esters having different viscosity to esters base oil, or by adding polymer, the viscosity is adjusted to obtain the lubricating oil suitable for various types of refrigerators. The lubricating oil thus obtained has excellent compatibility with 1,1,1,2-tetrafluoroethane refrigerant, which is an alternative to freon, and has low hygroscopic property and high heat-resistant property.
By reducing the total acid number to 0.05 mg KOH/g or less, the corrosion resistant property and insulating property of lubricating oil are not decreased, and the lubricating oil for refrigerator having high refrigerant stability, hydrolytic stability and insulating property can be obtained.
Further, by adding sulfur type anti-wear agent, the better anti-wear effect of the lubricating oil can be obtained on iron/aluminum contact portion in the refrigerator.
U.S. Pat. No. 5,211,884 (Bunemann et al., May 18, 1993) describes a lubricant/working fluid composition for use in mechanical vapor compression type heat transfer devices wherein the working fluid is preferably tetrafluoroethane and the lubricant is an ester which is miscible with the working fluid at 10% over a temperature range of xe2x88x9250xc2x0 C. to +80xc2x0 C., and has a viscosity of 5 to 100 cSt at 40xc2x0 C. Useful esters include pentaerythritol partial ester of straight chain C5 or branched chain C7 carboxylic acids. The esters are compatible with non-chlorine containing working fluids and exhibit a low level of corrosion.
U.S. Pat. No. 5,254,280 (Thomas et al., Oct. 19, 1993) is directed to polyoxyalkylene glycols which are used to flush currently used lubricants such as mineral oil, alkyl benzenes, and esters from a refrigeration system for conversion to fluorocarbon or hydrofluorocarbon refrigerants. The polyoxyalkylene glycol is selected from the group consisting of polyoxyalkylene glycol which is at least difunctional with respect to hydroxyl groups, polyoxyalkylene glycol having an alkyl cap on one end thereof, and polyoxyalkylene glycol having at least two alkyl caps. The polyoxyalkylene glycol has a molecular weight of about 300 to 4,000, has a viscosity of about 5 to 150 centistokes at 37xc2x0 C., and is made from alkylene oxide having at least 4 carbon atoms.
U.S. Pat. No. 5,369,287 (Sunaga et al., Nov. 29, 1994) relates to 1,1,1,2-tetrafluoroethane used in a refrigerator as the refrigerant, while a polyolester oil which is well compatible with the refrigerant is used as the base oil and a phenolic antioxidant, a specified amine and a phosphoric triester are added thereto to give a refrigerator oil composition. Thus the hydrolysis of the polyolester oil can be prevented to thereby protect the sliding members such as a roller and a vane from the corrosion and wear which are caused by the hydrolysis.
U.S. Pat. No. 5,395,544 (Hagihara et al., Mar. 7, 1995) is directed to a working fluid composition for a refrigerating machine which contains difluoromethane and a refrigeration oil. An ester formed between (a) an aliphatic polyhydric alcohol having a carbon number of 2 to 12; and (b) a saturated aliphatic monocarboxylic acid having a carbon number of 4 to 9 or a derivative thereof, the ratio of the number of acyl groups having a branched chain or branched chains to the number of the entire acyl groups in the ester being not less than 95%, is used as a base oil of the refrigeration oil. The working fluid composition for refrigerating machine of the present invention is excellent not only in compatibility, lubricity, and electric insulating property but also in thermal stability as compared to the conventional products.
U.S. Pat. No. 5,403,503 (Seiki et al., Apr. 4, 1995) discloses a refrigerator oil composition for hydrogen-containing hydrofluorocarbons (hydrogenated Flon compound) refrigerant which comprises a polyoxyalkylene glycol derivative and/or a specific polyester compound, which are/is compounded with (a) an aliphatic acid partially esterified with a polyhydric alcohol and (b) a phosphate compound and/or a phosphite compound. The refrigerator oil composition according to the present invention can be utilized as a refrigerator oil effective for improving wear resistance, especially that between aluminum material and steel material owing to the excellent miscibility with hydrogenated Flon refrigerant such as Flon 134a as well as prominent lubricant performance.
U.S. Pat. No. 5,431,835 (Katafuchi et al., Jul. 11, 1995) relates to a lubricant for refrigerating machines employing tetrafluoroethane or the like as a refrigerant which comprises as an essential component a base oil comprising (A) 40 to 95% by weight of a synthetic oil composed of a poly-xcex1-olefin and/or an ethylene/xcex1-olefin copolymer or a mixture of an alkyl-benzene and a poly-xcex1-olefin and/or an ethylene/xcex1-olefin copolymer and (B) 5 to 60% by weight of a fluidity improver composed of a polyoxyalkylene glycol compound, etc. The lubricant is used along with a refrigerant comprising a substituted flon compound such as 1,1,1,2-tetrafluoroethane (R-134a), and is excellent in the performance such as wear resistance, electrical insulating properties, hydrolytic stability, nonhydrogroscopicity, etc. and also in returnability of the lubricant. Thus, the lubricant is especially effective when used in automobile or household air conditioners, refrigerators, etc. having high industrial usefulness.
U.S. Pat. No. 5,554,311 (Katafuchi et al., Sep. 10, 1996) discloses a lubricant composition for compression-type refrigerating machines containing etra-fluoroethane or the like as a refrigerant and a lubricant comprising (A) 40 to 95% by weight of a synthetic oil composed of a poly-xcex1-olefin and/or an ethylene/xcex1-olefin copolymer or a mixture of an alkylbenzene and a poly-xcex1-olefin and/or an ethylene/xcex1-olefin copolymer and (B) 5 to 60% by weight of a fluidity improver composed of both or either of an ester compound and a triglyceride. The lubricant composition is excellent in the performance such as wear resistance, electrical insulating properties, hydrolytic stability, nonhygroscopicity, etc. and also in returnability of the lubricant composition. Thus, the lubricant is especially effective when used in automobile or household air condition, refrigerator, etc. having high industrial usefulness.
U.S. Pat. No. 5,705,086 (Ardito et al., Jan. 6, 1998) relates to esters that function as refrigeration lubricants in compression refrigeration units. The ester exhibits a balance of performance characteristics, notably in the combination of good miscibility, hydrolytic stability and wear resistance coupled with a viscosity within the range required in many commercial refrigeration units. These esters are of a hindered dihydric or trihydric alcohol such as trimethylolpentanediol and a fatty acid, where at least 80 number percent of the acyl groups are straight chain groups.
European Patent No. 377,122 (Kawaguchi et al., publication date 11.07.90) relates to a novel lubricating oil for refrigerators with compressor. More particularly, the reference relates to a lubricating oil for refrigerators with a compressor (compression-type refrigerators), comprising as the main component a polyoxyalkyleneglycol derivative having a high lubricating property as well as a favorable compatibility with hydrogen-containing flon compounds such as 1,1,1,2-tetrafluoroethane which can substitute for flon compounds such as dichlorodifluoromethane used as refrigerant and involved in environmental pollution problems.
WO 90/12849 (Jolley, International publication date 01.11.90) describes
(A) a major amount of at least one fluorine containing hydrocarbon containing one or two carbon atoms; and
(B) a minor amount of at least one soluble organic lubricant comprising at least one carboxylic ester of a polyhydroxy compound containing at least 2 hydroxy groups and characterized by the general formula
R[OC(O)R1]nxe2x80x83xe2x80x83(I)
wherein R is a hydrocarbyl group, each R1 is independently hydrogen, a straight chain lower hydrocarbyl group, a branched chain hydrocarbyl group, or a straight chain hydrocarbyl group containing from 8 to about 22 carbon atoms provided that at least one R1 group is hydrogen, a lower straight chain hydrocarbyl or a branched chain hydrocarbyl group, or a carboxylic acid- or carboxylic acid ester-containing hydrocarbyl group, and n is at least 2.
Liquid compositions also are described wherein the fluorine-containing hydrocarbons also contain other halogen such as chlorine. The liquid compositions are useful particularly as refrigeration liquids in refrigerators and air-conditioners including auto, home and industrial air-conditioners.
A lubricant-refrigerant composition is disclosed which comprises
(A) at least one fluorine-containing hydrocarbon refrigerant containing 1 to 3 carbon atoms, further wherein fluorine is the only halogen in said fluorine-containing hydrocarbon with the proviso that 1,1,1,2-tetrafluoroethane is not the sole refrigerant; and
(B) at least one lubricant comprising
(1) a hydrocarbyl substituted arene,
(2) a phosphate ester,
(3) an organic ester of a carboxylic acid and an alcohol,
(4) a perfluoropolyethylene,
(5) an ether of the structure 
xe2x80x83wherein R3 is hydrogen, a hydrocarbon group containing from 1 to 20 carbon atoms, or an alkyl substituted aromatic wherein the alkyl group contains from 1 to 12 carbon atoms, R4 is independently hydrogen, methyl or ethyl, R5 is hydrogen or a hydrocarbon group containing from 1 to 20 carbon atoms or an acyl group containing from 2 to 20 carbon atoms, b is an integer of from 1 to 10 and a is an integer such that the product of a and b is at least two;
(6) a polyether wherein the polyether is prepared by polymerizing an ether of the structure
CH2xe2x95x90CHR1Oxe2x80x94R2
xe2x80x83wherein R1 is hydrogen or an alkyl group containing from 1 to 4 carbon atoms and R2 is an aliphatic group containing from 1 to 4 carbon atoms,
(7) a polyalphaolefin; or
(8) a mineral oil;
xe2x80x83wherein at a temperature of xe2x88x9260xc2x0 C. or higher a phase separation occurs such that at least two phases are formed, said phases being a refrigerant rich phase and a lubricant rich phase, further wherein the lubricant rich phase resides below the refrigerant rich phase. This invention also relates to a method of separating a lubricant-refrigerant composition and returning a lubricant rich phase of the lubricant from a refrigerant rich phase of the refrigerant to a compressor, which comprises;
permitting a liquid phase separation between the lubricant rich phase and the refrigerant rich phase wherein at a temperature of above xe2x88x9260xc2x0 C. the lubricant rich phase resides below the refrigerant rich phase;
removing the lower layer lubricant rich phase away from the upper layer refrigerant rich phase, and
returning the lubricant rich phase to the compressor; wherein the refrigerant and lubricant comprise the aforementioned components (A) and (B). Further, this invention relates to a compression refrigeration system, comprising;
a compressor, a condenser, an oil return valve, an oil return line, an expansion valve and an evaporator wherein the system is charged with a composition comprising the aforementioned components (A) and (B).